Oil-impregnated sintered bearing

ABSTRACT

An object of the present invention is to provide an oil-impregnated sintered sliding bearing which has a large amount of the lubricating oil as a bearing element which has long life, has a small amount of scattered and lost lubricating oil, has a simple structure, and takes up a small space for a bearing. An oil-impregnated sintered sliding bearing includes: an axis; plural porous sintered compacts joined with each other by sizing; a cavity between the sintered compacts at an axial direction center portion; and a gap which continuously extends from an end portion of the cavity and has a width narrower than the cavity, wherein the gap opens to an end surface or a peripheral surface of the bearing.

TECHNICAL FIELD

The present invention relates to an oil-impregnated sintered slidingbearing, and in particular relates to an oil-impregnated sinteredsliding bearing which has a superior lifetime and has a simple structurethereof.

BACKGROUND ART

An oil-impregnated sintered sliding bearing is composed of a poroussintered alloy having pores in which lubricating oil is contained. Theoil-impregnated sintered sliding bearing has an open porosity of about15 to 30%. It is known that friction increases and seizure occurs incases in which about 50% of the lubricating oil in the pores is lost. Inorder to prevent the friction increase, means for increasing the amountof the lubricating oil which is a bearing element are as follows. (1) Afelt containing lubricating oil is provided outside an oil-impregnatedsintered sliding bearing (see Patent Document 1). (2) In producing anoil-impregnated sintered sliding bearing, a core of a material such as awax or a resin is embedded in a metal powder filled in a die, compactedand sintered with metal powder, and lubricating oil is contained in acavity that is formed by the core being vaporized or burned by sintering(see Patent Document 2).

Means for preventing leakage of lubricating oil are known as follows.(3) A sintered metal member for absorbing lubricating oil is provided soas to contact an end surface of an oil-impregnated sintered slidingbearing, wherein the sintered metal member is more porous than theoil-impregnated sintered sliding bearing (see Patent Document 3). (4)Recesses are provided concentrically or in all directions on a bearingend surface, and lubricating oil is held in the recesses by surfacetension of the lubricating oil (see Patent Document 4).

Patent Document 1 is Japanese Examined Utility Model ApplicationPublication No. S55-23064. Patent Document 2 is Japanese Examined PatentApplication Publication No. S28-4456. Patent Document 3 is JapaneseExamined Utility Model Application Publication No. H8-9450. PatentDocument 4 is Japanese Examined Utility Model Application PublicationNo. S53-53787.

DISCLOSURE OF THE INVENTION Problems Solved by the Invention

However, in general, in the technique using the felt as a supplying oilmeans except for the pores of the bearing, the felt is disposed on anoutside diameter side of the bearing, and lubricating oil is suppliedfrom an outside diameter surface of the bearing, but it is difficult toensure reliable adhesion between the felt and the bearing, and oilleakage possibly occurs from the felt. In the technique using the wax orthe resin to have the cavity for containing lubricating oil in thebearing, the lubricating oil in the cavity thermally expands when thetemperature of the bearing rises during the action of the bearing. Alarge amount of the lubricating oil, which is more than necessary, flowsfrom an inside peripheral surface and an end surface of the bearing. Thelubricating oil is scattered by a rotation of a shaft, and is lost. Thatis, in the cavity having a capillary attraction lower than on theperiphery thereof, the lubricating oil is merely lost and is replaced bythe air. When the shaft is rotated again in this condition, sincethermal expansion of the air in the cavity is relatively large, thelubricating oil in the oil-impregnated sintered sliding bearing isdischarged outside and is lost. As a result, expected effects bysecuring the lubricating oil in the cavity cannot be obtained. In thetechnique in which the porous sintered member or the felt for absorbingthe lubricating oil is provided in an edge surface of theoil-impregnated sintered sliding bearing as a means for securing thelubricating oil in the bearing element, since the porous sinteredmember, etc., are provided outside the bearing, the bearing elementhaving the bearing housing is large. In the technique using the recessesformed concentrically or in all directions on the bearing end surface,effects by preventing leakage of lubricating oil are small in cases inwhich the recesses are not deep. In particular, in compact bearings, itis difficult to form the recesses, so that effects by preventing leakageof lubricating oil cannot be obtained sufficiently.

As described above, the conventional techniques do not have the allcharacteristics that the amount of the lubricating oil as the bearingelement is large for a long lifetime of the bearing, a small amount ofthe lubricating oil is scattered and is lost, and the structure thereofis simple and compact. In recent years, the development of a productiontechnique for the oil-impregnated sintered sliding bearing having allthese characteristics is required.

The present invention was made in consideration of the aboverequirements. An object of the present invention is to provide anoil-impregnated sintered sliding bearing which can have a large amountof the lubricating oil as the bearing element so as to have longlifetime. An object of the present invention is to provide anoil-impregnated sintered sliding bearing in which the amount ofscattered and lost lubricating oil is small. An object of the presentinvention is to provide an oil-impregnated sintered sliding bearingwhich can have a simple structure and thereby reduce the space taken upthereby.

Means for Solving the Problems

According to one aspect of the present invention, as described in claim1, an oil-impregnated sintered sliding bearing includes: an axis; pluralporous sintered compacts joined with each other by sizing; a cavityprovided between the sintered compacts at a center portion of thebearing in a direction of the axis; and a gap extending continuouslyfrom an end portion of the cavity along the axis or in a radialdirection and having a width narrower than that of the cavity. The gaphas an opening at an end surface of the bearing or at a peripheralsurface of the bearing.

In this case, the above gap preferably has the following shape. That is,as described in claim 2, the gap may be at least one recess stripeprovided between an outside member of the sintered compacts and aninside member of the sintered compacts, or the gap may be composed ofrecess stripes which are provided between the outside member and theinside member and are gear-shaped in a plan view.

According to a preferred embodiment of the present invention, thebearing may have a housing, and the bearing and the housing may have thefollowing structures. That is, as described in claim 3, the bearing mayhave a spherical surface or a chamfer portion at an edge of theperipheral surface on a side of the opening of the gap, and an anglebetween the spherical surface or the chamfer portion and the insidesurface of the housing may be 45 degrees or less. Alternatively, asdescribed in claim 4, the bearing may have an outside diameter which issmaller than an inside diameter of the housing, or the bearing may haveplural recess stripes provided to an peripheral portion of the bearingso as to extend along the axis, so that another gap is formed betweenthe peripheral surface of the bearing and the inside surface of thehousing proximate to the opening of the gap.

According to a preferred embodiment of the oil-impregnated sinteredsliding bearing of the present invention, as described in claim 5, aninside member of the sintered compacts may project along the axis withrespect to an outside member of the sintered compacts on a side of theopening of the gap, so that the bearing has a step formed on the sidethereof. Alternatively, as described in claim 6, an inside member of thesintered compacts may have a flange portion at an end portion thereof ona side of the opening of the gap, and a ring-shaped gap may be formedamong an end surface of the outside member of the sintered compacts, alower surface of the flange portion of the inside member, and the insidesurface of the housing. Alternatively, as described in claim 7, theflange portion of the inside member may have an outside diameter smallerthan an inside diameter of the housing, or plural recess stripes may beprovided on a peripheral portion of the flange portion so as to extendalong the axis, so that another gap is formed between a peripheralsurface of the flange portion and the inside surface of the housing.

According to a preferred embodiment of the present invention, thebearing may have the following structure on an inside peripheralportion. That is, as described in claim 8, the bearing may have achamfer portion at an inside peripheral edge at least on a side of theopening of the gap, and may have a tapered shape at an inside peripheraledge of an end portion thereof, so that clearance between an insideperipheral surface of the bearing and a shaft inserted into the bearingat an end portion of a sliding surface is larger than that at a centerportion thereof. As described in claim 9, the bearing may have an insidediameter at least at the other end portion opposite to a side of theopening of the gap, the inside diameter being larger than those atportions other than the other end portion, so that clearance between aninside peripheral surface of the bearing and a shaft inserted into thebearing at an end portion of a sliding surface is larger than that at acenter portion thereof. As described in claim 10, the large insidediameter portion of the other end portion is formed by the outsidemember of the sintered compacts.

According to a preferred embodiment of the oil-impregnated sinteredsliding bearing of the present invention, as described in claim 11, aninside member of the sintered compacts may have an open porosity or anaverage pore diameter, which is smaller than that of the outside member.

EFFECTS OF THE INVENTION

In the oil-impregnated sintered sliding bearing of the presentinvention, lubricating oil is impregnated in the pores of the sinteredbearing, the cavity, and the gap. The sintered bearing is mounted to thehousing and is used. In initial running in the use, when the lubricatingoil is discharged to the surface thereof by temperature rise thereof dueto the rotation of the shaft, the lubricating oil is easily dischargedoutside the bearing via the gap. The lubricating oil is discharged tothe end surface portion on a side of the opening of the gap, and is heldby surface tension of the lubricating oil in a corner space portionbetween the housing and the end surface of the bearing, a corner spaceportion between the housing and the chamfer portion at the peripheraledge of the bearing, or a corner space portion between the sphericalsurface at the periphery of the bearing and the housing. In a case inwhich angle at the corner space portion is smaller, the lubricating oilis more sufficiently held. In particular, the angle is preferably 45degrees or less in order to sufficiently hold the lubricating oil in thecorner space portion due to the wettability of the lubricating oil.Although the minimum of the angle is not especially determined, theangle is preferably 25 degrees or more in order to hold sufficientamount of the lubricating oil in the depth of the corner space portion.

Since the lubricating oil held in the corner space portion contacts theperipheral surface of the sintered bearing, the lubricating oil isabsorbed from the pores of the sintered bearing by contraction of thelubricating oil in the sintered bearing due to temperature fall in stopof running or by capillary attraction working between the insides of thepores and the lubricating oil in order to solve a shortage of thelubricating oil in the sintered bearing. In this manner, the lubricatingoil held in the corner space portion contributes to supplying of thelubricating oil in the sintered bearing. Although the cavity and the gaphas a function for holding the lubricating oil at corner portions onwhich surface tension of the lubricating oil works, a large part of thelubricating oil is replaced by the air, so that the cavity and the gaplose the ability to hold the lubricating oil. In a cylindrical bearing,the opening of the gap is in the end surface of the bearing since theperiphery of the bearing is press-fitted in the housing. In a case inwhich in an aligning bearing, the spherical portion on the periphery ofthe bearing is opened from the housing, or lubricating oil can be heldon an inside wall surface of the housing, the opening can be in thespherical surface.

In the above manner, the cavity can be used for a oil reservoir only ininitial running in which the bearing is used, and the gap communicatingfrom the cavity to the surface is used for a guide passage through whichlubricating oil discharged from the bearing is supplied to apredetermined place more than other places. As a result, the lubricatingoil discharged from the bearing exists by surface tension of thelubricating oil proximately to a corner portion formed by the insidesurface of the housing and the end surface of the bearing without usingan oil absorber, for example, a felt. Therefore, scattering and loss ofthe lubricating oil can be inhibited. Even if a felt is provide to thecorner portion, scattering and loss of the lubricating oil can beinhibited, so that a felt can be provided thereto. In this case,scattering and loss of the lubricating oil can be more inhibited.

In the one aspect of the present invention, in addition to ensuringsufficient amount of the lubricating oil and inhibiting scattering andloss of the lubricating oil as described above, the oil-impregnatedsintered sliding bearing is formed by combining the plural poroussintered compacts by sizing, so that the structure of the bearing can besimple, and can thereby reduce space taken up thereby.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments will be explained hereinafter with reference to drawings.FIG. 1 is a schematic longitudinal-sectional view showing structures ofbearing elements in conditions in which an assembled oil-impregnatedsintered sliding bearing of the present invention is used. FIG. 2 is alongitudinal-sectional view of each member which is a component of thebearing. A bearing 1 is produced as described below. An inside member 3is fit into an outside member 2, the members 2 and 3 are integrallyjoined with each other by sizing in a die, or are mounted to a housing4, and the members 2 to 4 are subjected to sizing in a die.

The outside member 2 has a large diameter portion 2 a and a smalldiameter portion 2 b. The small diameter portion 2 b is connected withthe large diameter portion 2 a, and has a diameter smaller than that ofthe large diameter portion 2 a. The small diameter portion 2 b hasplural recess stripes 2 c which are formed on an inside peripherythereof, thereby being gear-shaped in a plan view (viewed from the leftside in FIG. 2). The outside member 2 has chamfer portions 2 d which areformed at peripheral edge portions thereof. The inside member 3 has asmall diameter portion 3 a and a large diameter portion 3 b. The largediameter portion 3 b is connected with the small diameter portion 3 a,and has a diameter larger than that of the small diameter portion 3 a.The large diameter portion 3 b has plural recess stripes 3 c which areformed on a periphery thereof. The outside member 2 and the insidemember 3 are sintered compacts. The members 2 and 3 are integrallyjoined with each other by compressing them in a die, a gap 5 is formedby the recess stripes 2 b and 3 b, and a cavity 6 is formed due todifference in length between step portions of the members 2 and 3. Thebearing 1 produced in the above manner is subjected to oil-impregnationprocess. The bearing 1 is mounted to the housing 4, and a shaft 7 isinserted into the bearing 1. Pores, the cavity 6, and the gap 5 of thebearing 1 are subjected to oil-impregnation process beforehand. Theamount of the lubricating oil contained in the cavity 6 of the bearing 1corresponds 100% of the amount of open pores based on open pores of atypical porous sintered bearing.

In the case in which the shaft 7 is rotated, a sliding surface islubricated by a lubricating mechanism specific to the oil-impregnatedsintered sliding bearing, the temperature of the bearing 1 rises by therotation of the shaft 7, so that the lubricating oil in the bearing 1 isexuded so as to flow to a bearing surface. In this case, in addition,the lubricating oil in the cavity 6 is discharged to an end surface ofthe bearing 1 via the gap 5 which is a thick passage. The dischargedlubricating oil is accumulated at corner portions which are formedbetween the housing 4 and the bearing 1, so that oil reservoirs 8 areformed. Oil volumes of the oil reservoirs 8 are increased by forming thechamfer portions 2 d. In a case in which an angle between the housing 4and each chamfer portion 2 d is set to 45 degrees or less, thelubricating oil can be sufficiently accumulated at the corner portionsdue to wettability of the lubricating oil. In a case in which an anglebetween the housing 4 and each chamfer portion 2 d is set to 25 degreesor more, the sufficient amount of the lubricating oil can be accumulatedat an innermost of each corner space portion.

When the rotation of the shaft 7 is stopped, the temperature of thebearing 1 is fallen, the pores of the bearing 1 absorbs the lubricatingoil which exists at the bearing surface and the oil reservoirs 8. Inorder to increase the absorbance of the oil and the accumulation amountof the oil, it is preferable that the outside member 2 be a sinteredcompact having open porosity greater than that of the inside member 3.The outside member 2 is composed of a sintered material different fromthat of the inside member 3 having the bearing sliding surface. As aresult, for example, the outside member 2 can be an inexpensive materialin comparison with the inside member 3, so that production cost can bereduced. When the lubricating oil is absorbed in the bearing 1,capillary attraction can hardly be worked in the cavity 6 and the gap 5,so that the lubricating oil discharged once hardly returns to the cavity6 and the gap 5, and is replaced by the air flowing from the gap 5, etc.In this manner, by performing initial running several times, the amountof the lubricating oil is appropriately balanced among the cavity 6, thegap 5, and the oil reservoirs 8.

In this manner, the cavity 6 and the gap 5 functions as oil reservoirsbefore the bearing elements are assembled, and the lubricating oil isaccumulated in the oil accumulation portions 8 outside the bearing 1 bythe rotation of the shaft 7. After the bearing elements are assembled,the amount of the lubricating oil in the bearing elements can berelatively large by this oil accumulation method without supplying thelubricating oil thereto, so that operation lifetime of theoil-impregnated sintered sliding bearing can be long.

FIG. 3 is a schematic longitudinal-sectional view showing bearingelements of an aligning bearing. FIG. 4 is a longitudinal-sectional viewshowing each member of a bearing 11 before sizing in production for thebearing 11 shown in FIG. 3. The bearing 11 can be formed as describedbelow. Sintered compacts of a recess member 12 and a protrusion member13 as shown in FIG. 4 are fit to each other, and are subjected tocompression sizing in a typical spherical die, and each peripherythereof is formed so as to have a spherical surface. The recess member12 has plural radial recess stripes 12 a which are formed at an endsurface portion thereof. The recess stripes 12 a face the protrusionmember 13, so that a gap 14 is thereby formed. A cavity 15 is a portionsurrounded by an inside peripheral step portion of the recess member 12and the protrusion member 13. In this example, the gap 14 opens to aperipheral spherical surface portion. By providing the recess stripeshown in FIG. 2, the gap 14 extending from the cavity 15 can be formedon a connecting surface parallel to an axis. The bearing 11 subjected tothe sizing and the oil-impregnation process is mounted to the housing16. A shaft 17 is inserted into the bearing 11. The action of thelubricating oil in the cavity 15 and the gap 14 by the operation of thebearing 11 is the same as that described above. The oil reservoirs 18are formed at space portions of which longitudinal sections of thecavity 15 and the gap 14 are triangle-shaped and proximate to an endsurface portion of the bearing 11.

FIG. 5 is a longitudinal-sectional view showing a spherical bearing 21which is a modification example of the spherical bearing 11 shown inFIG. 3. In this example, a gap 23 communicating from a cavity 22 to theoutside opens to an end surface side of the bearing 21, so that theexample shown in FIG. 5 is structured such that discharge of thelubricating oil on the end surface side is preceded differently from theexample shown in FIG. 3. The lubricating oil discharged in this mannerflows through a groove 21 a formed on a peripheral surface of thespherical bearing 21, and then is accumulated in a gap portion betweenthe spherical bearing 21 and a housing 24. In a case in which thehousing 24 has a structure shown in the Figure, the lubricating oil canbe accumulated in the gap portion. A felt can be appropriately providedto the gap portion. In a case in which a shaft 25 is used, thelubricating oil in the gap portion is absorbed from an oil reservoir 26to a outside member 27, and moves to an inside member 28 by a capillaryattraction. Therefore, on the end surface portion and inside thebearing, a mechanism in which the lubricating oil is circulated isobtained, and long lifetime of the oil-impregnated sintered slidingbearing is obtained. Since an inside diameter of the outside member 27is larger than that of the inside member 28, the other end surface canhave a function in which leakage oil flowing through the shaft 25 isabsorbed in the outside member 27. The lubricating oil moves to theinside member 28 by a capillary attraction in the same manner as thelubricating oil absorbed from the oil reservoir 26. In this manner, theoil circulating function can be obtained on the above other end surface.

FIGS. 6A to 6F are longitudinal-sectional schematic views showingcombination features of protrusion members (inside members) 33 a to 33 fand recess members (outside members) 34 a to 34 f for forming cavities31 a to 31 f and gaps 32 a to 32 f in cylindrical bearings. In theFigures, reference numerals 35 a to 35 c, 35 e, and 35 f show facingportions which are exposed on end surfaces between the members,reference numerals 36 a to 36 e are facing portions which are exposed onperipheries, and reference numerals 37 d and 37 f are facing portionsexposed on inside peripheries.

An example shown in FIG. 6A is a combination feature of the cylindricalprotrusion member 33 a and the recess member 34 a, wherein thecylindrical protrusion member 33 a has a flange and the recess member 34a has a chamfer portion on an end surface on an inside peripheral sidethereof. In this example, the cavity 31 a is surrounded by a smalldiameter portion and a large diameter portion of the protrusion member33 a, and a chamfer portion of the recess member 34 a, thereby beingtriangle-shaped in longitudinal section. The facing portions of themembers 33 a and 34 a are the facing portion 35 a exposed on the endsurface, and the facing portion 36 a exposed on the periphery. In eachfacing portion 35 a and 36 a, the gap 32 a may be formed therein ifnecessary.

An example shown in FIG. 6B is a combination feature of the members 33 band 34 b having substantially the same shapes as those of the exampleshown in FIG. 6A. The example shown in FIG. 6B differs from the exampleshown in FIG. 6A in that the end surface portion on the inside diameterside of the recess member 34 b is step-shaped, and the cavity 31 b issquare-shaped in longitudinal section. The combination feature shown inFIGS. 6A and 6B does not have a complicated shape, and can be easilyformed.

An example shown in FIG. 6C is a combination feature of the members 33 cand 34 c having shapes similar to those of the example shown in FIG. 6B.The example shown in FIG. 6C differs from the example shown in FIG. 6Bin that the periphery side of the protrusion member 33 c has threesteps, and the protrusion member 33 c and the recess member 34 c are fitin each other at two portions and are joined thereat. In the exampleshown in FIG. 6C, since the protrusion member 33 c has a complicatedshape and a thin wall thickness portion in comparison with the exampleshown in FIG. 6B, it is difficult to use this example for a compact sizebearing. However, since the members 33 c and 34 c are stronglyconnected, the example shown in FIG. 6C is desirably used for bearingshaving a gap which opens to one end surface thereof.

An example shown in FIG. 6D is a combination feature in which themembers 33 d and 34 d having shapes similar to those of the exampleshown in FIG. 6B. The example shown in FIG. 6D differs from the exampleshown in FIG. 6B in that a sliding surface 37 d comprises a portion ofthe recess member 34 d. In the example shown in FIG. 6D, portions atwhich the gap 32 d opens to a surface are the periphery 36 d and theinside periphery 37 d of the recess member 33 d. In the cylindricalbearing shown in FIG. 6D, for example, a recess groove (not shown) isrequired for forming an oil reservoir in a housing.

An example shown in FIG. 6E is a combination feature of the two outsidemembers 34 e having simple cylindrical shapes and the inside member 33 ehaving a simple cylindrical shape. The cavity 31 e is formed by achamfer portion which is on an inside diameter side of the outsidemember 34 e. The example shown in FIG. 6E has more members than theexamples shown in FIGS. 6A to 6D, but is easily produced regardless ofthe size of the bearing, since the shapes of the members are simple. Thegap 32 e can open to a periphery and an end surface of the bearing, andcan be selected in accordance with a purpose of using the bearing.

An example shown in FIG. 6F is a combination feature of the members 33 fand 34 f having the shapes similar to those of the example shown in FIG.6D. The example shown in FIG. 6F differs from the example shown in FIG.6D in that the gap 32 f opens to the end surface 35 f and the insideperiphery 37 f of the protrusion portion 33 f and the recess member 34f. In the example shown in FIG. 6F, for example, a recess groove (notshown in the Figure) is required for forming an oil reservoir in ahousing. It should be noted that in the respective features shown inFIGS. 6A to 6F, the respective members are repressed compacts (which aresubjected to sizing).

The bearings described above are basic types of the bearings of thepresent invention, and desirable embodiments of the present inventionwill be explained in detail, in which the above patterns are furthercombined.

FIG. 7 is a longitudinal-sectional view showing another desirableexample of a cylindrical bearing. The bearing of this example has aninside member 41 having a protruded shape and an outside member 42having a recessed shape, the members 41 and 42 being joined with eachother by sizing. In this example, a cavity 43, gaps 44 and 45, a step46, a large inside diameter portion 47, and a chamfer portion 48 areformed in the same manner as described above. By these respectivemembers, lubricating oil can be discharged outside the bearing, can beaccumulated in the bearing elements, and can be supplied from the oilreservoir to the oil-impregnated sintered bearing.

FIG. 8 is a longitudinal-sectional view showing another desirableexample of a cylindrical bearing. The bearing of this example has aninside member 51 having a protruded shape and an outside member 52having a recessed shape, the members 51 and 52 being joined with eachother by sizing. In this example, a cavity 53, the gaps 54 to 56,chamfering portions 57 and 58, and a flange portion 59 are formed in thesame manner as described above. In this example, by these respectivemembers, lubricating oil can be discharged outside the bearing, can beaccumulated in the bearing members, and can be supplied from the oilreservoir to the oil-impregnated sintered bearing.

FIG. 9 is a longitudinal-sectional view showing another desirableexample of an aligning bearing. The bearing of this example has aninside member 61 having a protruded shape and outside member 62 having arecessed shape, the members 61 and 62 being joined with each other bysizing. In this example, a cavity 63, gaps 64 to 66, and a chamferportion 67 are formed in the same manner as described above. In thisexample, by these respective members, lubricating oil can be dischargedoutside the bearing, can be accumulated in the bearing elements, and canbe supplied from the oil reservoir to the oil-impregnated sinteredbearing.

FIG. 10 is a longitudinal-sectional view showing another desirableexample of an aligning bearing. The bearing of this example has aninside member 71 having a protruded shape and an outside member 72having a recessed shape, and these members 71 and 72 being joined witheach other by sizing. In this example, a cavity 73, a gap 74, a step 75,a large diameter portion 76, and a chamfer portion 77 are formed in thesame manner as described above. In this example, by these respectivemembers, lubricating oil can be discharged outside the bearing, can beaccumulated in the bearing elements, and can be supplied from the oilreservoir to the oil-impregnated sintered sliding bearing.

INDUSTRIAL APPLICABILITY

As explained above, in the oil-impregnated sintered sliding bearing ofthe present invention having a simple structure, when the bearing isused, lubricating oil can be discharged outside the bearing via thepassage, can be accumulated in the bearing elements, and can be suppliedfrom the oil reservoir to the bearing. Therefore, the amount of thelubricating oil can be sufficiently secured without supplyinglubricating oil when the bearing is assembled. As a result, longoperating lifetime of the bearing can be obtained. Therefore, thepresent invention is promising in that the present invention can beapplied to oil-impregnated sintered sliding bearings which are desirablyused for various sintered mechanical parts.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a longitudinal-sectional view of bearing elements usingcylindrical bearing according to the present invention.

FIG. 2 is a longitudinal-sectional view of each member of the bearingshown in FIG. 1.

FIG. 3 is a longitudinal-sectional view of bearing elements using analigning bearing according to the present invention.

FIG. 4 is a longitudinal-sectional view of each member of the bearingshown in FIG. 3.

FIG. 5 is a longitudinal-sectional view of another of the bearingelements using an aligning bearing according to the present invention.

FIGS. 6A to 6F are longitudinal-sectional schematic views showingvarious combination features of members of a cylindrical bearing in acase in which the bearing is used.

FIG. 7 is a longitudinal-sectional view showing a desirable example of acylindrical bearing.

FIG. 8 is another longitudinal-sectional view showing another desirableexample of a cylindrical bearing.

FIG. 9 is a longitudinal-sectional view showing another desirableexample of an aligning bearing.

FIG. 10 is a longitudinal-sectional view showing another desirableexample of an aligning bearing.

EXPLANATION OF REFERENCE NUMERALS

-   -   1 bearing,    -   2 outside member,    -   2 d chamfer portion,    -   3 inside member,    -   4 housing,    -   5 gap,    -   6 cavity,    -   7 shaft,    -   8 oil reservoir

1. An oil-impregnated sintered sliding bearing comprising: an axis;plural porous sintered compacts joined with each other by sizing; acavity provided between the sintered compacts at a center portion of thebearing in a direction of the axis; and a gap continuously extendingfrom an end portion of the cavity along the axis or in a radialdirection and having a width narrower than that of the cavity, whereinthe gap has an opening at an end surface of the bearing or a peripheralsurface of the bearing.
 2. The oil-impregnated sintered sliding bearingaccording to claim 1, wherein the gap is at least one recess stripeprovided between an outside member of the sintered compacts and aninside member of the sintered compacts, or the gap is composed of recessstripes which are provided between the outside member and the insidemember and are gear-shaped in a plan view.
 3. The oil-impregnatedsintered sliding bearing according to claim 1, wherein the bearingfurther comprises a housing having an inside surface, and the bearinghas a spherical surface or a chamfer portion at an edge of theperipheral surface on a side of the opening of the gap, and an anglebetween the spherical surface or the chamfer portion and the insidesurface of the housing is 45 degrees or less.
 4. The oil-impregnatedsintered sliding bearing according to claim 1, wherein the bearingfurther comprises a housing having an inside surface, and the bearinghas an outside diameter which is smaller than an inside diameter of thehousing, or the bearing has plural recess stripes provided to anperipheral portion of the bearing so as to extend along the axis, sothat another gap is formed between the peripheral surface of the bearingand the inside surface of the housing proximate to the opening of thegap.
 5. The oil-impregnated sintered sliding bearing according to claim1, wherein an inside member of the sintered compacts projects along theaxis with respect to an outside member of the sintered compacts on aside of the opening of the gap, so that the bearing has a step formed onthe side of the opening.
 6. The oil-impregnated sintered sliding bearingaccording to one claim 1, wherein the bearing further comprises ahousing having an inside surface, an inside member of the sinteredcompacts has a flange portion at an end portion thereof on a side of theopening of the gap, and a ring-shaped gap is formed among an end surfaceof the outside member of the sintered compacts, a lower surface of theflange portion of the inside member, and the inside surface of thehousing.
 7. The oil-impregnated sintered sliding bearing according toclaim 6, wherein the flange portion of the inside member has an outsidediameter smaller than an inside diameter of the housing or plural recessstripes are provided on a peripheral portion of the flange portion so asto extend along the axis, so that another gap is formed between aperipheral surface of the flange portion and the inside surface of thehousing.
 8. The oil-impregnated sintered sliding bearing according toclaim 1, wherein the bearing has a chamfer portion at an insideperipheral edge at least on a side of the opening of the gap, and has atapered shape at an inside peripheral edge of an end portion thereof, sothat clearance between an inside peripheral surface of the bearing and ashaft inserted into the bearing at an end portion of a sliding surfaceis larger than that at a center portion thereof.
 9. The oil-impregnatedsintered sliding bearing according to claim 1, wherein the bearing hasan inside diameter at least at the other end portion opposite to a sideof the opening of the gap, the inside diameter being larger than thoseat portions other than the other end portion, so that clearance betweenan inside peripheral surface of the bearing and a shaft inserted intothe bearing at an end portion of a sliding surface is larger than thatat a center portion thereof.
 10. The oil-impregnated sintered slidingbearing according to claim 9, wherein the large inside diameter portionof the other end portion is formed by the outside member of the sinteredcompacts.
 11. The oil-impregnated sintered sliding bearing according toclaim 1, wherein an inside member of the sintered compacts has an openporosity or an average pore diameter, which is smaller than that of theoutside member.